“Entrance telephones” used today are either arranged with installed fixed communication circuits (“local telephones”) or connected to and switched through a public telephone network (“door telephones”). They exist basically due to a need for security and privacy while still offering a social possibility—for inhabitants in areas which require locked entrances due to various threats and risks in mainly highly populated areas, but they also involve certain disadvantages.
Local telephones are costly to install, wire and maintain; door telephones involve continuos costs for the building when used, and for reasons unknown are the local telecommunication authorities always attempting to create a number of obstacles for an economical installation. All of them include the disadvantage caused by externally available user units which are extremely sensitive for outer influence and vandalism, and, mainly for the same reason, most of these units are of loudspeaking types, “hands free”, and often having a poor sound quality.
However, today a large part of the population, and rapidly increasing, carry a radio telephone (“cellular phone”, “mobile (telephone)”), or may at least do so if there are sufficient reasons. These telephones have excellent communication, signalling and sound properties, but have so far lacked possibility of using these properties as a possibility to gain access/lock opening from a visitor's point of view.